Many devices, such as computers, tablets, smartphones, and gaming systems, allow users to touch or “click” on displayed objects in order to select an option or identify where additional input, such as keystrokes, should be entered. For example, the user may touch the display with his or her finger or use a pointer input, such as a mouse click or pen tap, to identify an area of interest on the display. A device may use hit testing to determine what area of the display has been selected and then perform additional operations based upon the object displayed in the selected area. For example, when the user has selected an input field (e.g., a text input field) on an application's display, the application is notified that additional input, such as a keyboard input, is associated with the selected input field. In a synchronous operating system, a central component performs this hit testing and determines what portion of a display has been selected.
In systems that allow for the simultaneous display of multiple application windows, the hit testing may determine not only what area has been selected, but may also determine which of two or more displayed applications is associated with the selected area. For example, different applications may be displayed in different windows with one of the windows being associated with a currently active application. The central component in a synchronous system receives all inputs and has knowledge about all displayed windows. This allows the user's pointer input to be easily be correlated with a target window so that non-active or non-selected windows can be activated when touched before additional input (e.g., keystrokes) are provided to the selected application.